Some current methods for verifying the identity of a printed item are generally based on overt or covert marks deliberately applied to an item, usually by printing. Other methods rely on natural variations in a material substrate (fiber orientation in paper, for example) to be used as a unique identifier. Significant deficiencies exist in the existing technology. These include the need to deliberately add overt or covert marks to the item in addition to any marks already present on the item for other purposes. In the case of the substrate variation method, a specialized system that perceives the variations is necessary. Also, for substrates that do not present a readily identifiable unique feature (some plastic films for example) this method cannot be employed. These deficiencies seriously reduce the utility of these methods in the technical fields considered here.